In order to float across land and water, the giant air-trapping skirt around the base of a hovercraft needs to keep a tight seal at all times. Were it to tackle giant waves, it would get tossed about just like a boat, but unlike a boat it would tend to sink—because that cushion of air would be gone. But an improved…»2/13/14 9:20am 2/13/14 9:20am